Solid state light amplifying device with sintered photoconductor



Nov. 24, 1964 MITSURU OIKAWA 3,158,747

SOLID STATE LIGHT AMPLIFYING DEVICE WITH SINTERED PHOTOCONDUCTOR Filed April 3, 1961 United States Patent Ofilice Patented Nov. 24, 1964 3,158,747 S61E33 STATE LIGHT DEVICE W El ill SWTERED PHOTGKIGNDUtJTQR Mitcnrn Oilrawa, Tokyo-to, Japan, assignor to liahnshilri Keisha Hitachi Seisahuslro, Tokyo-to, .lapan, a jointstock company of Japan Filed Apr. 3, 1961, Ser. No. 1%,344 Claims priority, application Japan, Apr. 9, F964), 21,034/60 4 Claims. (Cl. 250-213) This invention relates to solid light amplifying apparatuses, and more particularly it relates to a new and improved solid state light amplifying appmatus having high sensitivity.

The nature, objects, and details of the invention will become clearly apparent by reference to the following detailed description when taken in connection with the accompanying drawing in which the same or equivalent parts are designated by the same reference numerals or the same reference numerals with subscripts, and in which:

FIG. 1 is a diagrammatic perspec e view showing the composition of a conventional solid light amplifying apparatus; and

FIG. 2 is a diagrammatic perspective view illustrating one embodiment of the solid light amplifying apparatus of the present invention.

A solid state light amplifying apparatus, as understood in this disclosure, is composed principally of a combination of an electroluminescent layer, which is caused to luminesce by the impressing of voltage thereon, and a PhOtCCOBdUCLlVE layer, the electrical resistance of which is reduced when the said layer is illuminated by light, and electrodes arranged on both surfaces of the said combination. in general, such apparatuses of known construction have hitherto been constructed with photoconductive layers formed in the shape of ridges and ooves so that they will have high dark resistance and high light trans- .issivity, and with an electrode of wire forrn connected alon the apex of each said ridge. Such a construction is illustrated in FIG. 1 which shows a photoconductive layer 2 of grooved form placed on an electroluminescent layer 1, wire-form electrodes 3 along the ridges of the photoconductive layer 2, transparent electrode 4 placed beneath the electroluminescent layer 1 and on a glass plate 6, and a voltage source 5 connected between the electrodes 3 and electrode 4.

l leretofore, the above-mentioned photoconductive layer of grooved form has, in general, been fashioned from a synthetic resin in which fine particles of a photoconductive substance, such as CdS, ha e been dispersed. However, in order to provide a sullicient mechanical strength in the grooved form construction, it has heretofore been impractical to provide a sufficiently high concentration of the particles of the photoconductive substance. Accordingly, the conventional apparatuses of such construction have had the disadvantage of low sensitivity.

It is, therefore, an essential object of the present invention to provide a new and improved solid state light amplifying apparatus wherein the above-described disadvantage has been eliminated, and high sensitivity is obtained.

The said object as well as other objects and advantages have been attained in the present invention by forming the photoconductive layer by sintering and by the adaptation of a unique construction, as described below.

Referring to FIG. 2, the apparatus of the invention in the embodiment shown has a basic structure comprising a transparent glass plate 6, a transparent electrode of fiat plate form, and an electroluminescent layer, similarly as in the construction shown in FlG. 1. On the upper surface of the electroluminescent layer 1 are disposed split electrodes 7 in rows. Heat-resistant, insulating posts 8 are attached adhesively along the said rows. On the upper surface of each of these posts 8, a wire electrode 3:: and a photoconductive layer 2a are formed in the axial direction (direction of the row), and on the side surfaces of each post 8, auxiliary spit electrodes 7a are formed in such a manner as to confront and be aligned with the aforesaid split electrodes and, at the same time, to clamp the photoconductlve layer 2:: cetween themselves and the wire electrode 3a.

The heat-resistant, insulating post 8 is made of such a material as a ceramic bar, and the photoconductive layer 2a is formed on the upper surface of each post 8 by preparing a paste composed of a pulverized, photoconductive substance such as C65 and applying a coating of t is paste on the said upper surface, then placing the post 3 with the said coating in a furnace at a temperature f the order of 600 degrees C. to sinter and form the aid coating. The wire electrode 31: and the auxiliary split electrodes 7a are fastened to their respective surfaces in the axial di'ection by such procedure as spraying with sdver paint. The bottom surface of the post 3 is bonded to a row of split electrodes 7 by means of epoxy resin. Several of these heat-resistant, insulating posts 8, on each of which the sintered photoconductive layer 2a, wire electrode 3a, and auxiliary split electrodes in are formed in the above-described manner, are fabricated and bonded to all of the rows of split electrodes 7. Then electrical contact between each auxiliary split electrode 7a and its respectively confronting split electrode 7 is established by such means as silver paint.

If, in an apparatus constructed as described above, an electric power source 5 is connected across the wire electrodes 3a of all heat-resistan insulating posts 3 and the flat-plate electrode l, a voltage will be impressed on the electroluminescent layer 1 through the sintered photoconductive layers 2a, aux liary s1 electrodes 7a, and split electrodes 7, and the electroluminescent layer 1 will luminesce in accordance with the magnitudes of the resistances (varying with intensity of illumination) of the sintered photoconductive layers 2a.

Since, in the light amplifying apparatus of the present invention the use of heat-resistant, insulating posts makes possible the formation of sintered photocon uctive layers, the sensitivity obtainable thereby is much higher than that in a conventional case wherein use in made of a photoconductive layer formed by scattering a photoconductive substance in a synthetic resin. Moreover, since the light current which passes through the said sintered photoconductive layer of the present invention flows in a direction which is parallel to the illuminated surface, the resistance drop erfect due to illumination of the photoconductive layer is sharply sensitive. Accordingly, an even higher sensitivity is provided.

While in the foregoing disclosure an embodiment of the apparatus of the invention of rectangular shape was described by way of example, it will be apparent that many other shapes thereof may be used in the practice of the invention.

Since it is thus obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited to the details described herein except as set forth in appended claims.

What is claimed is:

1. A solid state light-amplifying apparatus, which comprises a heat resistant insulating post having on its top surface a photoconductive layer sintered in situ thereon, a first electrode on said layer and a second electrode on a side surface of said post, said photoconductive layer being positioned between and contacting said first and second electrodes, an electroluminescent layer having a third electrode on one surface, said insulating post being adhesively'bonded on said one surface of the electro- V luminescent layer with the second and third electrodes in electrical contact, a transparent electrode positioned on the opposite side of said electroluminescent layer and a voltage source connected across said first electrode and said transparent electrode, said voltage being applied through said photoconductive layer and. said second electrode to said electroluminescent layer.

2. A solid state light-amplifying apparatus as defined .by claim 1, wherein said insulating post is of ceramic material. Y

3. A solid state light-amplifying apparatus which cornprises, a plurality of heat-resistant, insulating posts each of which has formed thereon in situ a sintered photo- 7 conductive layer extending lengthwise along a top surface thereof, a line electrode contacting said layer along the said top surface and a plurality of discrete electrodes on the lateral side surfaces of each post contacting opposite sides of said conductive layer, an velectrolurriinescent layer having a plurality of discrete electrodes on one surface thereof, said plural heat-resistant insulating posts being mounted on said surface with the discrete electrodes of the post and conductive layer reseectively in Contact,

7 AIR-CHE R. BORCHELT,

to the luminescent layer.

4. A solid state light-amplifying apparatus as defined by claim 3, wherein said insulating posts are of ceramic material.

References Cited by the Examiner UNITED STATES PATENTS 2,839,690 6/58 Kazan 250-213 2,905,830 9/59 Kazan 250'213 2,973,436 2/61 Koury 2502'13 3,015,036 12/61 Butler 250-213 3,059,118 10/62 Koury 250-2l3 3,081,402 3/63 Van Santen 250.213

OTHER REFERENCES Nicoll: RCA Technical Note No. 375, June 1960.

RAH-"H G. NELSON, Primary Examiner.

JOHN W. HUCKERT,

Examiners. v 

1. A SOLID STATE LIGHT-AMPLIFYING APPARATUS, WHICH COMPRISES A HEAT RESISTANT INSULATING POST HAVING ON ITS TOP SURFACE A PHOTOCONDUCTIVE LAYER SINTERED IN SITU THEREON, A FIRST ELECTRODE ON SAID LAYER AND A SECOND ELECTRODE ON A SIDE SURFACE OF SAID POST, SAID PHOTOCONDUCTIVE LAYER BEING POSITIONED BETWEEN AND CONTACTING SAID FIRST AND SECOND ELECTRODES, AN ELECTROLUMINESCENT LAYER HAVING A THIRD ELECTRODE ON ONE SURFACE, SAID INSULATING POST BEING ADHESIVELY BONDED ON SAID ONE SURFACE OF THE ELECTROLUMINESCENT LAYER WITH THE SECOND AND THIRD ELECTRODES IN ELECTRICAL CONTACT, A TRANSPARENT ELECTRODE POSITIONED ON THE OPPOSITE SIDE OF SAID ELECTROLUMINESCENT LAYER AND A VOLTAGE SOURCE CONNECTED ACROSS SAID FIRST ELECTRODE AND SAID TRANSPARENT ELECTRODE, SAID VOLTAGE BEING APPLIED THROUGH SAID PHOTOCONDUCTIVE LAYER AND SAID SECOND ELECTRODE TO SAID ELECTROLUMINESCENT LAYER. 